Complementary metal oxide semiconductor (CMOS) is a building block for integrated circuits, and CMOS devices are scaled to smaller sizes for advanced performance targets. CMOS technology includes N-type metal oxide semiconductor (NMOS) and P-type metal oxide semiconductor (PMOS). For example, a metal-oxide-semiconductor field-effect transistor (MOSFET) is a transistor used for amplifying or switching electronic signals.
A CMOS transistor generally comprises a semiconductor substrate, a channel layer above the semiconductor substrate, a gate oxide layer and a gate electrode above the channel layer, a source region and a drain region above semiconductor substrate. Contacts are made to the gate electrode, and to both the source and drain regions, of the transistor. With the advent of high-k dielectric materials as the gate oxide in the CMOS process, metal gates or metal layers are used for such contacts in the devices.
After formation of such metal gates or metal layers, a dielectric material is deposited over the metallic surface. For example, silicon dioxide (SiO2) can be formed by depositing a silicon-containing precursor compound such as silane (SiH4) or dicholorosilane (SiH2Cl2) using a deposition method such as chemical vapor deposition (CVD) in the presence of an oxidizing reactant.